#include <iostream>
using namespace std;

char ch = '*';
void sub(int x, int y, char ch, double *z)
{
 	switch(ch)
  	{
    case '+': *z = x + y; break;
    case '-': *z = x - y; break;
    case '*': *z = x * y; break;
    case '/': *z = x / y; break;
    }
}

int main()
{
    double x, y;
    // sub(10, 20, ch, y);

    // sub(1.2 + 3.2, '+', &y);

    // sub(sub(1, 2, '+', &y), sub(3, 4, '+', &x), '-', &y);

    sub(10, 20, &x, ch);

    return 0;
}